Medium conveyance apparatus and image formation apparatus

ABSTRACT

A medium conveyance apparatus includes a conveyance mechanism to convey a medium along a main conveyance path from a front side to a rear side; a sub-conveyance unit including a sub-conveyance path parallel with the main conveyance path and configured to convey the medium along the sub-conveyance path from the rear side to the front side; a medium transport mechanism to transport the medium from the sub-conveyance path or the medium supply unit to the main conveyance path; and a support member supporting the sub-conveyance unit to be slidable toward the front side. The sub-conveyance unit includes: a plate member defining the sub-conveyance path; and a medium guide mechanism attached to one end of the plate member on the front side. The medium guide mechanism guides the medium from the medium supply unit to the medium transport mechanism, and the medium from the sub-conveyance path to the medium transport mechanism.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority based on 35 USC 119 from prior Japanese Patent Application No. 2013-118049 filed on Jun. 4, 2013, entitled “MEDIUM CONVEYANCE APPARATUS AND IMAGE FORMATION APPARATUS”, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This disclosure relates to a medium conveyance apparatus on which a medium conveyance unit for use to form images on both sides of a sheet-like medium is detachably mounted, and an image formation apparatus provided with the medium conveyance apparatus.

2. Description of Related Art

Some image formation apparatuses such as printers or copiers have a duplex printing function of forming images on both sides (front-side surface and back-side surface) of a sheet-like medium such as paper, in addition to a function of forming an image on one side thereof. For example, Patent Literature 1 (Japanese Patent Application Publication No. 2012-181387, FIG. 4 and paragraphs [0050] to [0052]) discloses an image formation apparatus having a duplex printing function.

In the image formation apparatus in Patent Literature 1, a conveyance unit (referred to as “duplex printing unit” in Patent Literature 1) is detachably attached to an apparatus main body in a slidable manner. After an image is formed on the front-side surface of a medium, the conveyance unit reverses the medium upside down in order to form an image on the back-side surface of the medium.

SUMMARY OF THE INVENTION

However, the conveyance unit cannot be easily detached from the apparatus main body.

An objective of one embodiment of the invention is to enable a conveyance unit to be easily dismounted.

An aspect of the invention is a medium conveyance apparatus for use in an image formation apparatus provided with: a main body including a front end and a rear end being opposed to each other, a medium supply unit disposed in the main body, and a process unit configured to process a medium conveyed along with a main conveyance path in the main body. The medium conveyance apparatus includes: a conveyance mechanism configured to convey the medium along with the main conveyance path from a front end side to a rear end side; a sub-conveyance unit including a sub-conveyance path provided in parallel with the main conveyance path, and configured to send out the medium processed in the process unit by conveying the medium along with the sub-conveyance path from the rear end side to the front end side; a medium transport mechanism configured to transport the medium sent out from either one of the sub-conveyance path and the medium supply unit to the main conveyance path; and a unit support member supporting the sub-conveyance unit such that the sub-conveyance unit is slidable to the front end side. The sub-conveyance unit includes: a plate member defining the sub-conveyance path; and a medium guide mechanism attached to one end of the plate member on the front end side. The medium guide mechanism guides the medium sent out from the medium supply unit to the medium transport mechanism, and the medium sent out from the sub-conveyance path to the medium transport mechanism.

According to the above aspect of the invention, the sub-conveyance unit can be easily dismounted together with the medium guide mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a principal configuration of an image formation apparatus according to a first embodiment of the invention;

FIG. 2 is an enlarged view of the sub-conveyance unit illustrated in FIG. 1;

FIG. 3 is a perspective view illustrating a configuration example of the sub-conveyance unit in the first embodiment;

FIG. 4 is another perspective view illustrating the configuration example of the sub-conveyance unit in the first embodiment;

FIG. 5 is a perspective view of the base unit in the first embodiment, including partial enlarged views VB and VC;

FIG. 6 is a perspective view of the medium transport mechanism in the first embodiment.

FIG. 7 is a perspective view illustrating a configuration in which the base unit, the sub-conveyance unit, and the medium transport mechanism in the first embodiment are integrated with one another, wherein FIG. 7 includes enlarged views of a portion VIIB and a portion VIIC;

FIG. 8 is a perspective view illustrating a configuration in which a part of the medium transport mechanism is omitted from the configuration illustrated in FIG. 7;

FIG. 9 is a view illustrating a positional relationship between a front surface cover and the sub-conveyance unit in the first embodiment;

FIG. 10A is a view illustrating a state of a main guide member that is pushed by a press member, and FIG. 10B is a view illustrating a state of the main guide member in which the pushed state is released;

FIG. 11 is a view illustrating a state of the main guide member when the front surface cover is in an open position;

FIG. 12 is a view illustrating a state in which the sub-conveyance unit is pulled out;

FIG. 13 is a schematic perspective view of a sub-conveyance unit according to a second embodiment;

FIG. 14 is a schematic perspective view of the base unit in the second embodiment;

FIG. 15 is a view illustrating a part of the sub-conveyance unit in the second embodiment being enlarged;

FIG. 16 is a view illustrating a relationship between a main guide member and a lift member in the second embodiment;

FIG. 17 is a view illustrating a situation in which the front surface cover is moved to a close position for the main guide member on the lift members; and

FIG. 18 is a view illustrating a situation in which the front surface cover is moved to the close position for the main guide member if no lift member is present.

DETAILED DESCRIPTION OF EMBODIMENTS

Descriptions are provided hereinbelow for embodiments based on the drawings. In the respective drawings referenced herein, the same constituents are designated by the same reference numerals and duplicate explanation concerning the same constituents is omitted. All of the drawings are provided to illustrate the respective examples only.

Hereinafter, various embodiments according to the invention are described with reference to the drawings.

Hereinafter, the same constituents are designated by the same reference numerals in all the drawings.

First Embodiment

FIG. 1 is a schematic cross-sectional view of a principal configuration of image formation apparatus 1 according to a first embodiment of the invention. As illustrated in FIG. 1, image formation apparatus 1 is provided with apparatus main body (frame) 10, and inside apparatus main body 10, medium storage cassette 20 that stores therein sheet-like media Pa as materials to be transferred, pickup roller 32 that picks up medium Pa from medium storage cassette 20, feed roller 33 and separation roller 23 that send out medium Pa one by one, medium guide mechanism 46 that guides medium Pa sent out by feed roller 33 and separation roller 23, and medium transport mechanism 50 that transports medium Pa passed through medium guide mechanism 46 to main conveyance path D0.

Apparatus main body 10 includes a front end (right side in the drawing) and a rear end (end disposed on the side opposite to the front end) that are opposed to each other. Image formation apparatus 1 is provided with a front surface cover on the front end side of apparatus main body 10, but FIG. 1 does not illustrate the front surface cover for convenience of explanation. The front surface cover is described later.

Medium house cassette 20 has a function of housing media Pa in a state of being accumulated on medium reception portion 21, and is detachably mounted to apparatus main body 10. One end of medium reception portion 21 is lifted upward by an elastic member (not illustrated). Recording medium Pa includes, for example, paper, synthetic paper, cardboard, specific paper, or a sheet-like medium such as a plastic film or cloth, but medium Pa is not limited thereto. A user can draw out medium storage cassette 20 in such a manner that the user grips handle portion 20 h of medium storage cassette 20 to slide medium storage cassette 20 from apparatus main body 10 in the direction of the front end side thereof.

Pickup roller 32 is capable of picking up medium Pa from medium storage cassette 20 by rotating in the counterclockwise direction in response to a rotation driving force transmitted from a drive motor (not illustrated). Feed roller 33 is capable of sending out medium Pa from medium storage cassette 20 to medium guide mechanism 46 by rotating in the counterclockwise direction in response to the rotation driving force transmitted from a drive motor (not illustrated). Separation roller 23 that sends out medium Pa one by one from medium storage cassette 20 is disposed at a position opposed to feed roller 33. Even if two or more pieces of media Pa are picked up inadvertently at one time from medium storage cassette 20, separation roller 23 can separate the two or more media Pa into each medium Pa piece.

Medium guide mechanism 46 includes main guide member 47 and sub-guide member 48 as illustrated in FIG. 1. Sub-guide member 48 is disposed at the rear end side (left side in the drawing) of main guide member 47 in apparatus main body 10 so as to form a clearance between sub-guide member 48 and main guide member 47. Main guide member 47 guides medium Pa, sent from medium storage cassette 20, through the clearance to an inlet-side end of medium transport mechanism 50.

As illustrated in FIG. 1, medium transport mechanism 50 includes a pair of lower registration roller 51 and lower pressurization roller 52 that are disposed at positions opposed to a tip part of main guide member 47. Medium transport mechanism 50 further includes a pair of upper registration roller 54 and upper pressurization roller 55 that are disposed on the downstream side in the medium conveyance direction. Lower registration roller 51 and upper registration roller 54 can respectively rotate in the counterclockwise direction in response to the rotation driving force transmitted from the drive motor (not illustrated). Lower pressurization roller 52 opposed to lower registration roller 51 is disposed so as to rotate together with lower registration roller 51, and upper pressurization roller 55 opposed to upper registration roller 54 is disposed so as to rotate together with upper registration roller 54. Lower registration roller 51 and lower pressurization roller 52 can convey medium Pa sent by medium guide mechanism 46 while correcting any misalignment of medium Pa. Moreover, upper registration roller 54 and upper pressurization roller 55 can transport medium Pa, sent by lower registration roller 51 and lower pressurization roller 52, to main conveyance path D0 while correcting any misalignment of medium Pa.

A pair of conveyance rollers 81A, 81B as a conveyance mechanism are disposed downstream of medium transport mechanism 50 in the medium conveyance direction. Conveyance rollers 81A, 81B convey medium Pa transported onto main conveyance path D0 from medium transport mechanism 50 toward process unit 60.

Meanwhile, multi-purpose tray (MPT) 25 can be mounted on the front end of apparatus main body 10. For example, the user can manually feed sheet-like medium Pa in MPT 25. Image formation apparatus 1 is provided with pickup roller 26, feed roller 27, and separation roller 28 that are used for sending medium Pa in MPT 25 to main conveyance path D0. Pickup roller 26 rotates in the clockwise direction in response to the rotation driving force transmitted from the drive motor (not illustrated) to pick up medium Pa from MPT 25. Feed roller 27 rotates in the clockwise direction in response to the rotation driving force transmitted from the drive motor (not illustrated) to send out medium Pa to a region between upper registration roller 54 and upper pressurization roller 55 in medium transport mechanism 50. Separation roller 28 that sends out medium Pa, picked up from MPT 25 one by one, is disposed at the position opposed to feed roller 27. Upper registration roller 54 and upper pressurization roller 55 can transport medium Pa sent from MPT 25 to main conveyance path D0.

Image formation apparatus 1 is further provided with process unit 60 and fuser 70 that are disposed along with main conveyance path D0. Process unit 60 operates in response to a control by a control circuit (not illustrated), and has a function of forming a developer image corresponding to image data in accordance with an electrophotographic method. Transfer roller 69 is disposed at a position opposed to process unit 60. Transfer roller 69 is a member that causes the developer image formed on process unit 60 to be transferred onto medium Pa.

Process unit 60 includes, as illustrated in FIG. 1, toner cartridge (developer storage container) 61 that stores therein a developer, photosensitive drum 62 serving as an image carrier, charge roller 63 serving as a charge unit that uniformly charges the surface of photosensitive drum 62, LED head (light exposure unit) 65 that exposes the surface of photosensitive drum 62 to light to form an electrostatic latent image on the surface of photosensitive drum 62, development roller (development unit) 67 serving as a developer carrier, and supply roller 66 that causes the developer supplied from toner cartridge 61 to be adhered on the surface of development roller 67. Photosensitive drum 62 has a cylindrical shape, and rotates in the clockwise direction, as shown by the arrow in element #62 in FIG. 1, in response to a rotation driving force transmitted from a drum motor (not illustrated). Photosensitive drum 62 is configured to include a metal pipe (conductivity base) such as aluminum, for example, and a light conductive layer, such as an organic photoconductor (OPC), that is formed around this metal pipe. Note that, process unit 60 further includes a development blade that reduces the thickness of the developer layer (toner layer) on the surface of development roller 67, but this development blade is not illustrated.

LED head 65 is disposed at a position opposed to and near to the surface of photosensitive drum 62. LED head 65 irradiates the surface of photosensitive drum 62 with pattern light corresponding to an image to be printed to form an electrostatic latent image on photosensitive drum 62. Such an LED head 65 can be configured to include a large number of LED elements (light-emitting diode elements) that are arranged along in the longitudinal direction of photosensitive drum 62 (vertical direction in the drawing), an LED drive circuit that drives these LED elements, and an array of optical lenses that guides emission light from these LED elements to the surface of photosensitive drum 62.

When a portion of the surface of photosensitive drum 62, on which an electrostatic latent image is formed, reaches development roller 67, a developer is transferred to the electrostatic latent image due to a potential difference between the electrostatic latent image on photosensitive drum 62 and development roller 67. This causes a developer image (toner image) to be formed on photosensitive drum 62. Thereafter, the developer image on photosensitive drum 62 is conveyed to a position (transfer position) opposed to transfer roller 69. Herein, the developer image on photosensitive drum 62 is transferred onto the surface of medium Pa by a transfer bias applied to transfer roller 69. A cleaning device, not illustrated, removes the developer that is not transferred onto the surface of medium Pa but remains on photosensitive drum 62.

Fuser 70 has a function of fixing the developer image on medium Pa that is sent from process unit 60 onto medium Pa. As illustrated in FIG. 1, fuser 70 includes fixation roller 71, pressurization roller 72 and auxiliary roller 73 that are disposed so as to be opposed to fixation roller 71. Fuser 70 further includes endless pressurization belt 74 that is wound around pressurization roller 72 and auxiliary roller 73 and is brought into pressure contact with the surface of fixation roller 71. A heat source (not illustrated) such as a halogen lamp is disposed inside fixation roller 71. Moreover, fixation roller 71 rotates in the clockwise direction in response to the rotation driving force transmitted from the drive motor (not illustrated). Fixation roller 71 and pressurization belt 74 apply heat and pressure to medium Pa sent to a nip part between pressurization belt 74 and fixation roller 71, so that the developer image on medium Pa can be fused and fixed on the medium Pa. Note that, fuser 70 illustrated in FIG. 1 is not limited thereto, and another fuser may be used in place of fuser 70.

Conveyance rollers 82A, 82B send medium Pa—out from fuser 70 to the rear end side of the apparatus (at the downstream side in the medium conveyance direction on main conveyance path D0). In this case, medium Pa is fed to either one of discharge conveyance path D1 and switchback conveyance path D2 in accordance with the positions of separators 88, 89. When medium Pa is supplied to discharge conveyance path D1, discharge rollers 83A, 83B, 84A, and 84B discharge medium Pa onto a medium placement surface of stacker unit 11.

In contrast, when image formation apparatus 1 operates in a duplex printing mode, medium Pa is supplied to switchback conveyance path D2 in order to form a printed image on a back-side surface of medium Pa. When medium Pa is supplied to switchback conveyance path D2, conveyance roller 85A, 85B, 86A, and 86B convey medium Pa upward on switchback conveyance path D2. Thereafter, the position of separator 89 is switched. Then, conveyance roller 85A, 85B, 86A, and 86B rotate in the reverse direction to convey medium Pa downward in apparatus main body 10. In this case, separator 89 and conveyance rollers 87A, 87B guide medium Pa to sub-conveyance path D3 that is provided in parallel with main conveyance path DO. Sub-conveyance path D3 is a conveyance path provided in order to convey medium Pa with one side (front-side surface) on which a printed image is formed to the front end side of the apparatus.

Note that, switchback conveyance path D2, switchback conveyance rollers 85A, 85B, 86A, and 86B, and separators 88, 89 can constitute a reverse conveyance mechanism of the invention.

Referring to FIG. 1, image formation apparatus 1 is provided with base unit 30 that is fixed to apparatus main body 10, and sub-conveyance unit 40 for duplex printing that is disposed on base unit 30 to be slidable to the front end side of the apparatus.

FIG. 2 is an enlarged view of sub-conveyance unit 40 illustrated in FIG. 1. FIG. 2 illustrates side surfaces of main guide member 47 and sub-guide member 48, and cross sections of components other than main guide member 47 and sub-guide member 48. In FIG. 2, a negative direction of an X axis corresponds to the conveyance direction of medium Pa on sub-conveyance path D3, a positive direction of a Z axis is vertical to the X axis direction and corresponds to the height direction of apparatus main body 10, and the Y axis direction is vertical to each of the X axis direction and the Y axis direction and corresponds to the transverse width direction of apparatus main body 10.

As illustrated in FIG. 2, sub-conveyance unit 40 includes guide plate member 41 serving as a plate member that constitutes sub-conveyance path D3, guide frame 42 that is disposed opposed to guide plate member 41, and pinch rollers 44, 45 that are disposed respectively opposed to conveyance rollers 34, 35. Herein, conveyance rollers 34, 35 are provided in base unit 30. Pinch rollers 44, 45 are biased toward conveyance rollers 34, 35, and supported rotatably together with conveyance rollers 34, 35. Conveyance rollers 34, 35 are capable of conveying medium Pa in sub-conveyance path D3 to the front end side of the apparatus by rotating in the clockwise direction in response to the rotation driving force transmitted from the drive motor (not illustrated).

Sub-guide member 48 is fixed to a front end of guide plate member 41. An inner surface of sub-guide member 48 (inner guide surface 48 a) guides medium Pa to the inlet-side end (region between lower registration roller 51 and lower pressurization roller 52) of medium transport mechanism 50. Further, an outer surface (outer guide surface 48 b) of sub-guide member 48 is opposed to main guide member 47, and forms the clearance through which medium Pa sent from medium storage cassette 20 passes.

The front and back sides of medium Pa that is sent to medium transport mechanism 50 from sub-conveyance path D3 are reversed. In this case, medium transport mechanism 50 feeds medium Pa in a state where the front-side surface is directed downward and the back-side surface is directed upward to main conveyance path D0. This enables process unit 60, transfer roller 69, and fuser 70 to form a printed image on the back-side surface of medium Pa.

Tip part 47 t of main guide member 47 in a use state illustrated in FIG. 2 is pushed toward the rear end side of the apparatus, which is described later, and thus main guide member 47 is in a state where main guide member 47 cannot rotate. Meanwhile, when the pushing is released, main guide member 47 can rotate around shaft portion 47 s in the outer direction. In this state, since tip part 47 t of main guide member 47 separates from lower registration roller 51 and lower pressurization roller 52, the user can slide the entire sub-conveyance unit 40 to the front end side of the apparatus, which is described later, and dismount sub-conveyance unit 40 to the outside through opening portion P0 in FIG. 1. Hereinafter, a configuration of sub-conveyance unit 40 is described in detail.

FIG. 3 and FIG. 4 are perspective views illustrating a configuration example of sub-conveyance unit 40. FIG. 3 is the perspective view of sub-conveyance unit 40 viewed from the forward and diagonally upper side, and FIG. 4 is the perspective view of sub-conveyance unit 40 viewed from the rearward and diagonally upper side.

As illustrated in FIG. 3 and FIG. 4, sub-conveyance unit 40 is configured to include guide plate member 41, side frames 43L, 43R that are fixed to both side ends (both ends in the Y axis direction) of guide plate member 41 and are opposed to each other, guide frame 42 that is opposed to an upper surface of guide plate member 41 and is fixed between side frames 43L, 43R, sub-guide member 48 that is fixed to the front end of guide plate member 41, main guide member 47 that is turnably attached to the front end of guide plate member 41, and pinch rollers 44, 45 that are attached to an approximate central part of guide frame 42. Guide plate member 41 can be made using a plate material made of a metal. Moreover, side frames 43L, 43R, guide frame 42, main guide member 47 and sub-guide member 48 can be made by resin molding.

When medium Pa is conveyed in sub-conveyance path D3, medium Pa reaching sub-conveyance unit 40 is firstly carried on rear end 41 b of guide plate member 41, then passes through a space between guide plate member 41 and guide frame 42, and thereafter, passes from front end 41 f of guide plate member 41 over sub-guide member 48.

Side frames 43L, 43R extend in the X axis direction, and are shaped to be left-right symmetric to each other. As illustrated in FIG. 3, handle portions 43Lh, 43Rh are respectively formed in the front ends of side frames 43L, 43R. As described later, the user can grip handle portions 43Lh, 43Rh to slide sub-conveyance unit 40. Moreover, as illustrated in FIG. 4, ribs 43Lg, 43Rg are respectively formed in side frames 43L, 43R. Ribs 43Lg, 43Rg extend from portions near the front end 41 f of guide plate member 41 to portions near the rear end 41 b thereof. In addition, as illustrated in FIG. 3 and FIG. 4, posts 43Lp, 43Rp that protrude in the sides are respectively formed in the rear ends of side frames 43L, 43R. Posts 43Lp, 43Rp and ribs 43Lg, 43Rg are parts that are guided by guide grooves of rail frames 36L, 36R (FIG. 5) of base unit 30, which is described later.

Moreover, as illustrated in FIG. 4, protrusion portions 43Lu, 43Ru that protrude rearward (in the positive direction of the X axis) are respectively formed on the back sides of handle portions 43Lh, 43Rh. Protrusion portions 43Lu, 43Ru are respectively to be engaged with engagement holes 56Lh, 56Rh (FIG. 6) of main frames 56L, 56R in medium transport mechanism 50, which is described later, and are formed in order to position sub-conveyance unit 40 with respect to medium transport mechanism 50.

Engagement portions 47 a, 47 b are respectively formed at both ends in the transverse width direction (Y axis direction) of main guide member 47. Engagement portions 47 a, 47 b protrude from a main body unit of main guide member 47 to the sides thereof. As illustrated in FIG. 3, engagement portions 47 a, 47 b are parts that abut on and engage with base ends of handle portions 43Lh, 43Rh. Engagement portions 47 a, 47 b are provided in order to regulate the rotation of main guide member 47.

Next, a configuration of base unit 30 serving as a unit support member that supports sub-conveyance unit 40 is described in detail.

FIG. 5 is a perspective view of base unit 30 viewed from the forward and diagonally upper side, wherein a portion VB and a portion VC are partial enlarged views of base unit 30. Base unit 30 can constitute the unit support member of the invention.

As illustrated in FIG. 5, base unit 30 is configured to include base plate member 31, rail frames 36L, 36R that are fixed to portions near both side ends (both ends in the Y axis direction) of base plate member 31 and are opposed to each other, conveyance rollers 34, 35, pickup roller 32, and feed roller 33. Base plate member 31 can be made using a plate material made of a metal. Rail frames 36L, 36R can be made using a metal or resin material.

Rail frames 36L, 36R have guide structures at inner surfaces thereof in which side frames 43L, 43R in sub-conveyance unit 40 illustrated in FIG. 3 and FIG. 4 are respectively guided and engaged. As illustrated in FIG. 5, guide groove 36Rg that extends in the X axis direction is formed on the inner surface of rail frame 36R that is one of the rail frames. Projection part 36Rt illustrated in enlarged view VB in FIG. 5 is formed near a front end of guide groove 36Rg. The user can insert post 43Rp and rib 43Rg of side frame 43R in sub-conveyance unit 40 into guide groove 36Rg over projection part 36Rt, and engage them with guide groove 36Rg. Moreover, as illustrated in enlarged view VC in FIG. 5, post reception portion 36Rp for engaging post 43Rp that is inserted into guide groove 36Rg is formed, and torsion spring 37R is disposed in a rear end of guide groove 36Rg. The inner surface of rail frame 36L that is the other rail frame has a guide structure similar to that of the inner surface of rail frame 36R. Thus, the user can guide and engage post 43Lp and rib 43Lg of side frame 43L in sub-conveyance unit 40 to and with the guide structure of rail frame 36L.

Further, as illustrated in FIG. 5, drive shafts 38A, 38B, and 38C for rotating conveyance rollers 34, 35 are attached to rail frame 36L. Drive shaft 38A transmits a rotation driving force transmitted from the drive motor (not illustrated) to drive shaft 38B via endless belt 39A. Drive shaft 38B is connected to a shaft portion of conveyance roller 34. Moreover, drive shaft 38B transmits the rotation driving force to drive shaft 38C via endless belt 39B. Drive shaft 38C is connected to a shaft portion of conveyance roller 35. This allows conveyance rollers 34, 35 to rotate in accordance with the rotation driving force transmitted from the drive motor and in synchronization with each other.

Next, a configuration of medium transport mechanism 50 is described in detail. FIG. 6 is a perspective view of medium transport mechanism 50 viewed from the forward and diagonally upper side.

As illustrated in FIG. 6, medium transport mechanism 50 includes L-character shaped main frames 56L, 56R that are opposed to each other in the Y axis direction, lower registration roller 51, lower pressurization roller 52, upper registration roller 54, upper pressurization roller 55, and guide frame 53. Main frames 56L, 56R can be made using a plate material made of a metal, and guide frame 53 can be made by resin molding.

Lower registration roller 51 includes shaft portion 51 s that is turnably supported by main frames 56L, 56R, and sub registration rollers 51A, 51B that commonly use shaft portion 51 s. Moreover, lower pressurization roller 52 includes shaft portion 52 s that is turnably disposed by main frames 56L, 56R, and sub pressurization rollers 52A, 52B, and 52C that commonly use shaft portion 52 s. Meanwhile, upper registration roller 54 includes shaft portion 54 s that is turnably supported by main frames 56L, 56R. Upper pressurization roller 55 includes shaft portion 55 s that is turnably supported by main frames 56L, 56R.

Engagement holes 56Lh, 56Rh are formed in main frames 56L, 56R. Engagement holes 56Lh, 56Rh respectively engage with protrusion portions 43Lu, 43Ru (FIG. 4) in sub-conveyance unit 40. Moreover, abutted portions 53Lc, 53Rc are provided at inner sides of main frames 56L, 56R. Abutted portions 53Lc, 53Rc prevent a rotation movement of main guide member 47 toward the rear end side of the apparatus (inner direction).

FIG. 7 is a perspective view illustrating a configuration in which base unit 30, sub-conveyance unit 40, and medium transport mechanism 50 are integrated with one another, wherein portions VIIB and VIIC are partial enlarged views of the configuration illustrated in FIG. 7. FIG. 8 is a perspective view illustrating a configuration in which main frame 56L in medium transport mechanism 50 is omitted from the integrated configuration illustrated in FIG. 7. Such base unit 30, sub-conveyance unit 40, and medium transport mechanism 50 can constitute a medium conveyance apparatus of the invention.

Placement portions 31 a, 31 b are respectively formed at both ends in the transverse width direction in a tip part of base plate member 31 in base unit 30 illustrated in FIG. 5. Main frames 56L, 56R in medium transport mechanism 50 illustrated in FIG. 6 are respectively placed in and fixed to placement portions 31 a, 31 b. Sub-conveyance unit 40 is inserted into and attached to base unit 30 through a space directly below guide frame 53 in medium transport mechanism 50.

In the configuration of FIG. 7, post 43Rp and rib 43Rg of side frame 43R in sub-conveyance unit 40 are slide-inserted into and held by guide groove 36Rg (FIG. 5) of rail frame 36R in base unit 30. Simultaneously, post 43Lp and rib 43Lg of side frame 43L as the other side frame in sub-conveyance unit 40 are slide-inserted into and held by a guide groove of rail frame 36L as the other rail frame in base unit 30.

Moreover, protrusion portions 43Ru, 43Lu (FIG. 4) formed on the back sides of handle portions 43Rh, 43Lh are respectively engaged with engagement holes 56Rh, 56L (FIG. 6) of main frames 56R, 56L in medium transport mechanism 50. In addition, as illustrated in enlarged views VIIB and VIIC in FIG. 7, engagement portions 47 a, 47 b that are both ends in the width direction in main guide member 47 are respectively engaged with inner edge parts of handle portions 43Lh, 43Rh. This regulates the rotation of main guide member 47 in the outer direction.

Image formation apparatus 1 described above is provided with a front surface cover that covers the front end of apparatus main body 10 (FIG. 1). FIG. 9 is a view illustrating a positional relationship among front surface cover 90, base unit 30, sub-conveyance unit 40, and medium transport mechanism 50. In FIG. 9, main frame 56L in medium transport mechanism 50 is not illustrated for a more convenient explanation. Moreover, only bottom part 10 b among parts in apparatus main body 10 is illustrated.

As illustrated in FIG. 9, front surface cover 90 is turnably attached to bottom part 10 b of apparatus main body 10. Moreover, front surface cover 90 is supported to be movable between a position illustrated by a solid line (hereinafter, referred to as “close position) and a position illustrated by a dashed line (hereinafter, referred to as “open position”).

Front surface cover 90 includes protruded press member 91 at the inner side of front surface cover 90. When front surface cover 90 is positioned in the close position, press member 91 pushes the back face (outer surface) of main guide member 47 to bias main guide member 47 to the rear end side of the apparatus. In this case, main guide member 47 rotates in the inner direction and is pushed toward abutted portions 53Lc, 53Rc (FIG. 6) in medium transport mechanism 50. This accurately fixes a position of tip part 47 t of main guide member 47 with respect to medium transport mechanism 50 and sub-conveyance unit 40 (in particular, a nip part between lower registration roller 51 and lower pressurization roller 52). In other words, main guide member 47 in this case is in a locked state. FIG. 10A is a view illustrating a state of main guide member 47 that is pushed by press member 91. As illustrated in FIG. 10A, elastic member 93, such as a coil spring, biases a base end of press member 91.

In contrast, when front surface cover 90 is positioned in the open position, as illustrated in FIG. 10B, main guide member 47 is turnable around shaft portion 47 s (the locked state of main guide member 47 is released). In this case, main guide member 47 can rotate in a direction (outer direction) to be away from the nip part between lower registration roller 51 and lower pressurization roller 52. FIG. 11 a view illustrating a state of main guide member 47 when front surface cover 90 is positioned in the open position. In this state, no interference object is present in a direction along which sub-conveyance unit 40 is drawn out. Thus, the user can draw out sub-conveyance unit 40 to the outside by griping handle portions 43Lh, 43Rh in sub-conveyance unit 40, and sliding sub-conveyance unit 40 toward the front end side of the apparatus, as illustrated in FIG. 12. Accordingly, sub-conveyance path D3 in sub-conveyance unit 40 is exposed to the user who operates at the front end side of the apparatus. Thus, the user can easily remove medium Pa in a jam state, for example.

When sub-conveyance unit 40 is moved back to an original state, the user may slide sub-conveyance unit 40 to a position where sub-conveyance unit 40 abuts on medium transport mechanism 50, and push it into the apparatus. Further, the user can fix the position of tip part 47 t of main guide member 47 to a position at which tip part 47 t directs the inlet-side end (the nip part between lower registration roller 51 and lower pressurization roller 52) in medium transport mechanism 50 by positioning the front surface cover 90 in the close position.

As described above, with image formation apparatus 1 in the first embodiment, medium guide mechanism 46 including main guide member 47 and sub-guide member 48 is attached to one end at the front end side in sub-conveyance unit 40. Sub-conveyance unit 40 is slidably supported by base unit 30. This allows the user to slide sub-conveyance unit 40 together with medium guide mechanism 46 to easily take out sub-conveyance unit 40 to the front end side of the apparatus, as illustrated in FIG. 12.

Moreover, image formation apparatus 1 is designed in such a manner that the user (operator) is likely to manually operate at the front end side of apparatus main body 10 (right side in the drawing). Specifically, the user can pull out medium storage cassette 20 in the direction of the front end side of the apparatus to add media Pa or resolve the jam state of medium Pa, and manually feed a medium to MPT 25 that is provided at the front end of the apparatus. In addition, discharge rollers 84A, 84B discharge medium Pa on which a printed image is formed, onto stacker unit 11 in the direction of the front end side. Accordingly, the user can more easily recognize and take out medium Pa on stacker unit 11 at the front end side of the apparatus (at the upstream side in the medium conveyance direction on main conveyance path D0) than at the rear end side of the apparatus (at the downstream side in the medium conveyance direction on main conveyance path D0). In addition, the user can move front surface cover 90 to the open position at the front end side of the apparatus, and then slide and dismount sub-conveyance unit 40 to the outside (FIG. 11 and FIG. 12). Herein, the user does not need to remove only medium guide mechanism 46 in advance before removing sub-conveyance unit 40. Further, the dismount direction of sub-conveyance unit 40 is the same as the pull-out direction of medium storage cassette 20. In this manner, the user can operate image formation apparatus 1 at the front end side of the apparatus without moving to the rear end side of the apparatus. This can provide image formation apparatus 1 with excellent operability compared with the related art.

Moreover, medium guide mechanism 46 (main guide member and sub-guide member 48) has a function of merging sub-conveyance path D3 that is a conveyance path for sending back medium Pa to the front end side of the apparatus, with a conveyance path for conveying medium Pa picked up from medium storage cassette 20. Medium guide mechanism 46 is disposed near the front end of apparatus main body 10. As illustrated in FIG. 12, the user can slide sub-conveyance unit 40 to dismount medium guide mechanism 46 to the outside. This results in easy maintenance of medium guide mechanism 46.

Moreover, in order to guide medium Pa to an accurate position, tip part 47 t of main guide member 47 is necessary to be disposed with high position accuracy with respect to the inlet-side end in medium transport mechanism 50 (the nip part between lower registration roller 51 and lower pressurization roller 52). In the embodiment, when front surface cover 90 is in the close position, as illustrated in FIG. 10A, press member 91 of front surface cover 90 pushes main guide member 47 toward abutted portions 53Lc, 53Rc (FIG. 6) in medium transport mechanism 50. Thus, tip part 47 t of main guide member 47 can be moved close to the inlet-side end of medium transport mechanism 50, and be positioned with high accuracy.

In contrast, when front surface cover 90 is moved from the close position to the open position, as illustrated in FIG. 10B, the fixed state of main guide member 47 is released, and tip part 47 t of main guide member 47 separates from the nip part between lower registration roller 51 and lower pressurization roller 52. This can prevent lower pressurization roller 52 from being an interference object when the user draws out sub-conveyance unit 40.

Second Embodiment

Next, a second embodiment according to the invention is described. FIG. 13 is a schematic perspective view of sub-conveyance unit 140 for duplex printing incorporated into an image formation apparatus in the second embodiment. Moreover, FIG. 14 is a schematic perspective view of base unit 130 incorporated into the image formation apparatus in the embodiment. The configuration of the image formation apparatus in the embodiment is similar to the configuration of the image formation apparatus in the first embodiment, except for including sub-conveyance unit 140 of FIG. 13 and base unit 130 of FIG. 14 in place of sub-conveyance unit 40 and base unit 30 in the first embodiment.

Sub-conveyance unit 140 includes, as illustrated in FIG. 13, main guide member 147 that is turnably attached to the front end of guide plate member 41, and protrusion portions 34Ra, 34La (turn regulation ribs) that regulate the rotation of main guide member 147 in the outer direction. Protrusion portions 34Ra, 34La are added to the inner surfaces of handle portions 43Rh, 43Lh. The configuration of sub-conveyance unit 140 in the embodiment is the same as the configuration of sub-conveyance unit 40, except for main guide member 147 and protrusion portions 34Ra, 34La.

Main guide member 47 described above in the first embodiment includes, as illustrated in FIG. 3, engagement portions 47 a, 47 b that abut on the edge parts of handle portions 43Lh, 43Rh. Meanwhile, the configuration of main guide member 147 in the embodiment is the same as the configuration of main guide member 47 in the first embodiment, except that main guide member 147 in the embodiment does not include such engagement portions 47 a, 47 b.

In the embodiment, protrusion portions 34Ra, 34La are added to the inner surfaces of handle portions 43Rh 43Lh in place of engagement portions 47 a, 4 7 b. This allows a wider clearance width between main guide member 147 and sub-guide member 48 in the fixed state, compared with that in the first embodiment, because of the expanded range in which main guide member 147 can rotate. FIG. 15 is a view illustrating protrusion portion 34Ra that is added to the inner surface of handle portion 43Rh as one of the handle portions by being enlarged.

Moreover, the configuration of base unit 130 in the embodiment is the same as the configuration of base unit 30 in the first embodiment except that, as illustrated in FIG. 14, lift members 136L, 136R are added to the tip parts of base unit 130. Lift members 136L, 136R have slanted surfaces on which abase end of main guide member 147 ascends when sub-conveyance unit 140 is slid rearward on base unit 130. FIG. 16 is a view illustrating a positional relationship between main guide member 147 and lift member 136L. As illustrated in FIG. 16, when sub-conveyance unit 140 is slid rearward, the base end of main guide member 147 firstly ascends on front slanted surface 136Lt of lift member 136L, and then is guided to flat surface 136Lf of lift member 136L.

FIG. 17 is a view illustrating a situation in which front surface cover 90 is moved to a close position for main guide member 147 on lift members 136L, 136R. As illustrated in FIG. 17, when front surface cover 90 is positioned in the close position, press member 91 provided at the inner surface of front surface cover 90 can push the back face of main guide member 147 to bias main guide member 147 to the rear end side of the apparatus, as in the case of the first embodiment. If lift members 136L, 136R were not provided, as illustrated in FIG. 18, main guide member 147 would largely rotate in the outer direction. In this case, even if front surface cover 90 were moved to the close position, press member 91 could not come into contact with main guide member 147.

As described above, with the image formation apparatus in the second embodiment, the user can easily take out medium Pa in a jam state between main guide member 147 and sub-guide member 48, because of the wider clearance width between main guide member 147 and sub-guide member 48 when sub-conveyance unit 140 is pulled out from apparatus main body 10. Moreover, press member 91 can push main guide member 147 when front surface cover 90 is moved to the close position because lift members 136L, 136R are provided.

MODIFICATION EXAMPLES OF FIRST AND SECOND EMBODIMENTS

In the foregoing, although the various embodiments according to the invention are described with reference to the drawings, these embodiments are merely examples of the invention, and various forms other than the abovementioned embodiments can be employed. For example, the image formation apparatuses in the first and the second embodiments each include one process unit 60 mounted thereon, and thus have only a function of forming a monochromatic printed image, but the invention is not limited thereto. An image formation apparatus that forms a color printed image can be implemented by preparing multiple process units that are arranged along with main conveyance path D0.

Moreover, the image formation apparatuses in the first and the second embodiments employ a direct transfer method to transfer a developer image onto medium Pa, but the invention is not limited thereto. The structure in which a developer image is transferred onto medium Pa by an intermediate transfer method may be employed.

Note that, in the first embodiment, medium transport mechanism 50 cannot be drawn out to the outside together with sub-conveyance unit 40 because medium transport mechanism 50 is fixed to base unit 30, but the invention is not limited thereto. The structure in the first embodiment may be modified in such a manner that sub-conveyance unit 40 and medium transport mechanism 50 are integrated to allow medium transport mechanism 50 to be drawn out to the outside together with sub-conveyance unit 40.

Further, the printers as image formation apparatuses are exemplified and described in the first and the second embodiments, but the invention is not limited to the printers, and can be applied to copiers, facsimile equipment, or multi function peripherals (MFPs). Note that, the MFP is an image formation apparatus having multiple functions, such as a copier, a printer, an image scanner, and facsimile equipment.

The invention includes other embodiments in addition to the above-described embodiments without departing from the spirit of the invention. The embodiments are to be considered in all respects as illustrative, and not restrictive. The scope of the invention is indicated by the appended claims rather than by the foregoing description. Hence, all configurations including the meaning and range within equivalent arrangements of the claims are intended to be embraced in the invention. 

1. A medium conveyance apparatus for use in an image formation apparatus provided with: a main body including a front end and a rear end being opposed to each other, a medium supply unit disposed in the main body, and a process unit configured to process a medium conveyed along with a main conveyance path in the main body, the medium conveyance apparatus comprising: a conveyance mechanism configured to convey the medium along with the main conveyance path from a front end side to a rear end side of the main body; a sub-conveyance unit including a sub-conveyance path provided in parallel with the main conveyance path, and configured to send out the medium processed in the process unit by conveying the medium along with the sub-conveyance path from the rear end side to the front end side; a medium transport mechanism configured to transport the medium sent out from either one of the sub-conveyance path and the medium supply unit to the main conveyance path; and a unit support member supporting the sub-conveyance unit such that the sub-conveyance unit is slidable to the front end side, wherein the sub-conveyance unit includes: a plate member defining the sub-conveyance path; and a medium guide mechanism attached to one end of the plate member on the front end side, and the medium guide mechanism is configured to guide the medium sent out from the medium supply unit to the medium transport mechanism, and the medium sent out from the sub-conveyance path to the medium transport mechanism.
 2. The medium conveyance apparatus according to claim 1, wherein the medium guide mechanism includes: a main guide member configured to guide the medium sent out from the medium supply unit to the medium transport mechanism; and a sub-guide member configured to guide the medium sent out from the sub-conveyance path to the medium transport mechanism, wherein the sub-guide member is disposed at the rear end side of the main guide member to form a clearance between the sub-guide member and the main guide member, and the main guide member is configured to guide the medium sent out from the medium supply unit to pass the medium though the clearance.
 3. The medium conveyance apparatus according to claim 2, wherein the sub-guide member includes: an inner guide surface configured to guide the medium sent out from the sub-conveyance path to the medium transport mechanism; and an outer guide surface opposed to the main guide member to form the clearance.
 4. The medium conveyance apparatus according to claim 2, wherein the front end of the main body includes: an opening portion opposed to one end of the sub-conveyance unit; and a front surface cover supported to be movable between a close position where the front surface cover closes the opening portion and an open position where the front surface cover opens the opening portion, the main guide member is turnably attached to the one end of the plate member, and the front surface cover fixedly biases the main guide member toward the rear end side when being positioned in the close position, and leaves the main guide member turnable without biasing the main guide member when being positioned in the open position.
 5. The medium conveyance apparatus according to claim 4, wherein the front surface cover includes a press member configured to bias the main guide member toward the rear end side when being positioned in the close position.
 6. The medium conveyance apparatus according to claim 4, wherein the main guide member is rotatable in a direction to enlarge the clearance along with the movement of the front surface cover from the close position to the open position.
 7. The medium conveyance apparatus according to claim 1, further comprising a lift member including slanted surfaces on which an end of the main guide member ascends along with a slide operation of the sub-conveyance unit from the front end side to the rear end side.
 8. The medium conveyance apparatus according to claim 1, wherein the front end of the main body includes: an opening portion opposed to one end of the sub-conveyance unit; and a front surface cover supported to be movable between a close position where the front surface cover closes the opening portion and an open position where the front surface cover opens the opening portion.
 9. The medium conveyance apparatus according to claim 1, further comprising a reverse conveyance mechanism configured to reverse front and back sides of the medium on which a printed image is formed, and then supply the medium to the sub-conveyance path.
 10. The medium conveyance apparatus according to claim 1, wherein the process unit forms a printed image on the medium in accordance with an electrophotographic method.
 11. An image formation apparatus, comprising: a main body including a front end and a rear end being opposed to each other; a medium supply unit disposed in the main body; a process unit configured to process a medium conveyed along with a main conveyance path in the main body; a conveyance mechanism configured to convey the medium along with the main conveyance path from a front end side to a rear end side; a sub-conveyance unit including a sub-conveyance path provided in parallel with the main conveyance path, and configured to send out the medium processed in the process unit by conveying the medium along with the sub-conveyance path from the rear end side to the front end side; a medium transport mechanism configured to transport the medium sent out from either one of the sub-conveyance path and the medium supply unit to the main conveyance path; and a unit support member configured to support the sub-conveyance unit is slidable to the front end side, wherein the sub-conveyance unit includes: a plate member configured to constitute the sub-conveyance path; and a medium guide mechanism attached to one end of the plate member on the front end side, and the medium guide mechanism guides the medium sent out from the medium supply unit to the medium transport mechanism, and the medium sent out from the sub-conveyance path to the medium transport mechanism.
 12. The image formation apparatus according to claim 11, wherein the medium guide mechanism includes: a main guide member configured to guide the medium sent out from the medium supply unit to the medium transport mechanism; and a sub-guide member configured to guide the medium sent out from the sub-conveyance path to the medium transport mechanism, the sub-guide member is disposed at the rear end side of the main guide member to form a clearance between the sub-guide member and the main guide member, and the main guide member guides the medium sent out from the medium supply unit to pass the medium though the clearance.
 13. The image formation apparatus according to claim 12, wherein the front end of the main body includes: an opening portion opposed to one end of the sub-conveyance unit; and a front surface cover supported to be movable between a close position where the front surface cover closes the opening portion and an open position where the front surface cover opens the opening portion, the main guide member is turnably attached to the one end of the plate member, and the front surface cover fixedly biases the main guide member toward the rear end side when being positioned in the close position, and leaves the main guide member turnable without biasing the main guide member when being positioned in the open position.
 14. The image formation apparatus according to claim 11, further comprising a lift member including slanted surfaces on which an end of the main guide member ascends along with a slide operation of the sub-conveyance unit from the front end side to the rear end side.
 15. The image formation apparatus according to claim 11, further comprising a reverse conveyance mechanism configured to reverse front and back sides of the medium on which a printed image is formed, and then supply the medium to the sub-conveyance path. 